JWKS - OpenID Connect Authentication

The JWKS (JSON Web Key Set) endpoint and functionality returns a JWKS containing public keys that enable clients to validate a JSON Web Token (JWT) issued by CAS as an OpenID Connect Provider.

The following settings and properties are available from the CAS configuration catalog:

The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

  • cas.authn.oidc.jwks.jwks-file=file:/etc/cas/config/keystore.jwks

    • Path to the JWKS file resource used to handle signing/encryption of authentication tokens.

    This setting supports the Spring Expression Language.

    org.apereo.cas.configuration.model.support.oidc.OidcJsonWebKeystoreProperties.
    The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value.

  • cas.authn.oidc.jwks.jwks-cache-expiration=PT60M

    • Timeout that indicates how long should the JWKS file be kept in cache.

    This settings supports the java.time.Duration syntax [?].

    org.apereo.cas.configuration.model.support.oidc.OidcJsonWebKeystoreProperties.
  • cas.authn.oidc.jwks.jwks-key-id=cas

    • The key identifier to set for the generated key in the keystore.

    org.apereo.cas.configuration.model.support.oidc.OidcJsonWebKeystoreProperties.
  • cas.authn.oidc.jwks.jwks-key-size=2048

    • The key size for the generated jwks. This is an algorithm-specific metric, such as modulus length, specified in number of bits.

    If the keystore type is EC, the key size defined here should switch to one of 256, 384 or 521. If using EC, then the size should match the number of bits required.

    org.apereo.cas.configuration.model.support.oidc.OidcJsonWebKeystoreProperties.
  • cas.authn.oidc.jwks.jwks-type=RSA

    • The type of the JWKS used to handle signing/encryption of authentication tokens. Accepted values are RSA or EC.

    org.apereo.cas.configuration.model.support.oidc.OidcJsonWebKeystoreProperties.

    Configuration Metadata

    The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

    Be Selective

    This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

    YAGNI

    Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

    Naming Convention

    Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc. When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.S ettings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

    Validation

    Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

    Indexed Settings

    CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

    Keystores

    CAS expects a single global keystore to load and use for signing and encryption operations of various tokens. In addition to the global keystore, each registered application in CAS can optionally contain its own keystore as a jwks resource.

    The following strategies can be used to generate a keystore.

    Default

    By default, a global keystore can be expected and defined via CAS properties. The format of the keystore file is similar to the following:

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    {
  "keys": [
    {
      "d": "...",
      "e": "AQAB",
      "n": "...",
      "kty": "RSA",
      "kid": "cas"
    }
  ]
}

    CAS will attempt to auto-generate a keystore if it can’t find one at the location specified in settings. If you wish to generate one manually, a JWKS file can be generated using this tool or this tool.

    Clustered Deployments

    When deploying CAS in a cluster, you must make sure all CAS server nodes have access to and share an identical and exact copy of the keystore file. Keystore differences will lead to various validation failures and application integration issues.

    Key Rotation

    Allowing CAS to rotate keys in the keystore is only applicable and relevant with this option, where CAS is in charge of the keystore location and generation directly. If you outsource the keystore generation task, you are also taking on the responsibility of rotation.

    This keystore is cached, and is then automatically watched and monitored by CAS for changes. As changes are detected, CAS will invalidate the cache and will reload the keystore once again.

    REST

    Keystore generation can be outsourced to an external REST API. Endpoints must be designed to accept/process application/json and generally should return a 2xx response status code.

    The following requests are made by CAS to the endpoint:

    Operation Parameters Description Result
    GET N/A Retrieve the keystore. 2xx status code; JWKS resource in response body.

    The following settings and properties are available from the CAS configuration catalog:

    The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

  • cas.authn.oidc.jwks.rest.url=

    • The endpoint URL to contact and retrieve attributes.

    org.apereo.cas.configuration.model.support.oidc.RestfulOidcJsonWebKeystoreProperties.
    The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value.

  • cas.authn.oidc.jwks.rest.basic-auth-password=

    • If REST endpoint is protected via basic authentication, specify the password for authentication.

    org.apereo.cas.configuration.model.support.oidc.RestfulOidcJsonWebKeystoreProperties.
  • cas.authn.oidc.jwks.rest.basic-auth-username=

    • If REST endpoint is protected via basic authentication, specify the username for authentication.

    org.apereo.cas.configuration.model.support.oidc.RestfulOidcJsonWebKeystoreProperties.
  • cas.authn.oidc.jwks.rest.headers=

    • Headers, defined as a Map, to include in the request when making the REST call. Will overwrite any header that CAS is pre-defined to send and include in the request. Key in the map should be the header name and the value in the map should be the header value.

    org.apereo.cas.configuration.model.support.oidc.RestfulOidcJsonWebKeystoreProperties.
  • cas.authn.oidc.jwks.rest.method=GET

    • HTTP method to use when contacting the rest endpoint. Examples include GET, POST, etc.

    org.apereo.cas.configuration.model.support.oidc.RestfulOidcJsonWebKeystoreProperties.

    Configuration Metadata

    The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

    Be Selective

    This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

    YAGNI

    Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

    Naming Convention

    Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc. When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.S ettings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

    Validation

    Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

    Indexed Settings

    CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

    Groovy

    Keystore generation can be outsourced to an external Groovy script whose body should be defined as such:

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    import org.apereo.cas.oidc.jwks.*
import org.jose4j.jwk.*

def run(Object[] args) {
    def logger = args[0]
    logger.info("Generating JWKS for CAS...")
    def jsonWebKeySet = "{ \"keys\": [...] }"
    return jsonWebKeySet
}

    The following settings and properties are available from the CAS configuration catalog:

    The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

  • cas.authn.oidc.jwks.groovy.location=

    • The location of the resource. Resources can be URLS, or files found either on the classpath or outside somewhere in the file system.

    org.apereo.cas.configuration.model.SpringResourceProperties.
    The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value.

    Configuration Metadata

    The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

    Be Selective

    This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

    YAGNI

    Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

    Naming Convention

    Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc. When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.S ettings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

    Validation

    Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

    Indexed Settings

    CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

    Custom

    It is possible to design and inject your own keystore generation strategy into CAS using the following @Bean that would be registered in a @Configuration class:

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    @Bean(initMethod = "generate")
public OidcJsonWebKeystoreGeneratorService oidcJsonWebKeystoreGeneratorService() {
    return new MyJsonWebKeystoreGeneratorService(...);
}

    Your configuration class needs to be registered with CAS. See this guide for better details.

    Key Rotation

    Key rotation is when a key is retired and replaced by generating a new cryptographic key. Rotating keys on a regular basis is an industry standard and follows cryptographic best practices.

    You can manually rotate keys periodically to change the JSON web key (JWK) key, or you can configure the appropriate schedule in CAS configuration so it would automatically rotate keys for you.

    Rotation Guidance

    NIST guidelines seem to recommend a rotation schedule of at least once every two years. In practice, modest CAS deployments in size and scale tend to rotate keys once every six months, either manually or automatically on a schedule.

    Keys that are generated by CAS and put into the keystore carry an extra state parameter that indicates the lifecycle status of the assigned key. The following values are accepted lifecycle states:

    Value Description
    0 The key is active and current, used for required operations.
    1 The key is will be the next key used during key rotation.
    2 The key is no longer used and active, and will be removed after revocation operations.

    CAS always signs with only one signing key at a time, typically the very first key listed and loaded from the keystore, that is deemed active and current judging by the state parameter. For backward compatibility, the absence of this parameter indicates that the key is active and current.

    The dynamic discovery endpoint will always include both the current key and the next key, and it may also include the previous key(s) if the previous key has not yet been revoked. To provide a seamless experience in case of an emergency, client applications should be able to use any of the keys specified in the discovery document.

    The following settings and properties are available from the CAS configuration catalog:

    The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

    The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value.

  • cas.authn.oidc.jwks.revocation.schedule.enabled=true

    • Whether scheduler should be enabled to schedule the job to run.

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.revocation.schedule.enabled-on-host=.*

    • Overrides SchedulingProperties#enabled property value of true if this property does not match hostname of CAS server. This can be useful if deploying CAS with an image in a statefulset where all names are predictable but where having different configurations for different servers is hard. The value can be an exact hostname or a regular expression that will be used to match the hostname.

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.revocation.schedule.repeat-interval=PT2M

    • String representation of a repeat interval of re-loading data for an data store implementation. This is the timeout between consecutive job’s executions.

    This settings supports the java.time.Duration syntax [?].

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.revocation.schedule.start-delay=PT15S

    • String representation of a start delay of loading data for a data store implementation. This is the delay between scheduler startup and first job’s execution

    This settings supports the java.time.Duration syntax [?].

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.rotation.schedule.enabled=true

    • Whether scheduler should be enabled to schedule the job to run.

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.rotation.schedule.enabled-on-host=.*

    • Overrides SchedulingProperties#enabled property value of true if this property does not match hostname of CAS server. This can be useful if deploying CAS with an image in a statefulset where all names are predictable but where having different configurations for different servers is hard. The value can be an exact hostname or a regular expression that will be used to match the hostname.

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.rotation.schedule.repeat-interval=PT2M

    • String representation of a repeat interval of re-loading data for an data store implementation. This is the timeout between consecutive job’s executions.

    This settings supports the java.time.Duration syntax [?].

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.
  • cas.authn.oidc.jwks.rotation.schedule.start-delay=PT15S

    • String representation of a start delay of loading data for a data store implementation. This is the delay between scheduler startup and first job’s execution

    This settings supports the java.time.Duration syntax [?].

    org.apereo.cas.configuration.model.support.quartz.SchedulingProperties.

    Configuration Metadata

    The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

    Be Selective

    This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

    YAGNI

    Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

    Naming Convention

    Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc. When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.S ettings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

    Validation

    Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

    Indexed Settings

    CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

    Custom

    It is possible to design and inject your own key rotation and revocation strategy into CAS using the following @Bean that would be registered in a @Configuration class:

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    @Bean
public OidcJsonWebKeystoreRotationService oidcJsonWebKeystoreRotationService() {
    return new MyJsonWebKeystoreRotationService();
}

    Your configuration class needs to be registered with CAS. See this guide for better details.

    Actuator Endpoints

    The following endpoints are provided by CAS:

    Rotate keys in the keystore forcefully.

    ResponseEntity application/json

    OidcJwksRotationEndpoint.handleRotation()
    org.apereo.cas.oidc.web.controllers.jwks.OidcJwksRotationEndpoint

    Revoke keys in the keystore forcefully.

    ResponseEntity application/json

    OidcJwksRotationEndpoint.handleRevocation()
    org.apereo.cas.oidc.web.controllers.jwks.OidcJwksRotationEndpoint